Heat input reduction in fillet welding using bypass and root opening

Submerged arc welding (SAW) of fillet welds is one of the major applications in the shipbuilding industry. Due to the requirement for the weld size, a sufficient amount of metal must be deposited. In a conventional SAW process, the heat input is proportional to the amount of metal melted and is thus determined by the required weld size. To meet this requirement, an excessive amount of heat is applied causing large distortions in the welded structures whose follow-up straightening is very costly. In order to reduce the needed heat input, double-electrode technology has been previously practiced creating the double-electrode SAW (DE-SAW) method for fillet welds. However, the reduction in the heat input also reduces the penetration capability. The ability to produce required weld beads is compromised. In this study, the authors propose to introduce a root opening in a T-joint between the flat and perpendicular panels forming a modified fillet weld design. Experimental results verified that the use of a root opening improves the ability of DESAW to produce the required weld beads at reduced heat input and penetration capability. Major parameters including the root opening, travel speed, and heat input have been selected/optimized/minimized to produce required fillet weld beads with a minimized heat input based on qualitative and quantitative analyses.